Innovations in diagnosing and verifying the level of success of treatment of cardiovascular disease have migrated from external imaging processes to internal, catheterization-based, diagnostic processes. Diagnosis of cardiovascular disease has been performed through angiogram imaging wherein a radiopaque dye is injected into a vasculature and a live x-ray image is taken of the portions of the cardiovascular system of interest. Magnetic resonance imaging (MRI) has also been utilized to non-invasively detect cardiovascular disease. Diagnostic equipment and processes also have been developed for diagnosing vasculature blockages and other vasculature disease by means of ultra-miniature sensors placed upon a distal end of a flexible elongate member such as a catheter, or a guide wire used for catheterization procedures.
One such ultra-miniature sensor device is a pressure sensor mounted upon the distal end of a guide wire. An example of such a pressure sensor is provided in Corl et al. U.S. Pat. No. 6,106,476, the teachings of which are expressly incorporated herein by reference in their entirety. Such intravascular pressure sensor measures blood pressure at various points within the vasculature to facilitate locating and determining the severity of stenoses or other disruptors of blood flow within the vessels of the human body. Such devices are presently used to determine the need to perform an angioplasty procedure by measuring blood pressure within a vessel at multiple locations, including both upstream and downstream of a stenosis and measuring a pressure difference that indicates the severity of a partial blockage of the vessel.
In particular, a guide wire mounted pressure sensor is utilized to calculate fractional flow reserve (or “FFR”). In the coronary arteries, FFR is the maximum myocardial flow in the presence of stenosis divided by the normal maximum myocardial flow. This ratio is approximately equal to the mean hyperemic (i.e., dilated vessel) distal coronary pressure Pd divided by the mean arterial pressure Pa. Pd is measured with a pressure sensor mounted upon a distal portion of guide wire or other flexible elongate member after administering a hyperemic agent into the blood vessel causing it to dilate. Pa is measured using a variety of techniques in areas proximal of the stenosis, for example, in the aorta.
FFR provides a convenient, cost-effective way to assess the severity of coronary and peripheral lesions, especially intermediate lesions. FFR provides an index of stenosis severity that allows rapid determination of whether an arterial blockage is significant enough to limit blood flow within the artery, thereby requiring treatment. The normal value of FFR is about 1.0. Values less than about 0.75 are deemed significant and require treatment. Treatment options include angioplasty and stenting.
Another such known ultra-miniature sensor device is a Doppler blood flow velocity sensor mounted upon the end of a guide wire. Such device emits ultrasonic waves along the axis of a blood vessel and observes a Doppler-shift in reflected echo waves to determine an approximation of instantaneous blood flow velocity. A Doppler transducer is shown in Corl et al. U.S. Pat. No. 6,106,476 on a guide wire that also carries a pressure transducer. Such devices are presently used to determine the success of a treatment to lessen the severity of a vessel blockage.
In particular, a Doppler transducer sensor is utilized to measure Coronary Flow Reserve (or “CFR”). CFR is a measure for determining whether a stenosis is functionally significant after treatment (e.g., post-angioplasty). CFR comprises a ratio of the hyperemic average peak velocity of blood flow to the baseline (resting) average peak velocity. Instantaneous peak velocity (IPV) is the peak observed velocity for an instantaneous Doppler spectrum provided by a Doppler transducer. An exemplary method of calculating an average peak velocity (APV) comprises averaging a set of IPV's over a cardiac cycle.
A known technique for determining whether an angioplasty was effective was to perform angioplasty, wait a few days, then perform thalium scintigraphy (imaging). If the angioplasty procedure was not effective, then re-intervention was performed and the lesion was again treated via angioplasty. On the other hand, using CFR, a flow measurement is taken immediately after angioplasty or stenting. The flow measurement is utilized to determine whether adequate flow has been restored to the vessel. If not, the balloon is inflated without the need for secondary re-intervention. A normal CFR is greater than about 2 and indicates that a lesion is not significant. Lower values may require additional intervention. In addition to being used post-treatment to determine the efficacy of treatment, CFR may be measured prior to treatment to determine if treatment is required.
A guide wire combination device, comprising a pressure sensor and a flow sensor having substantially different operational characteristics, was disclosed in the Corl et al. U.S. Pat. No. 6,106,476. While it has been proposed within the Corl et al. U.S. Pat. No. 6,106,476 to combine pressure and flow sensors on a single flexible elongate member, the prior art does not address how such a combination sensor is coupled to consoles that display an output corresponding to the signals provided by the flexible elongate member corresponding to the sensed pressure and flow within a vessel. Indeed, the relevant art comprises special-purpose monitors having static display interfaces that display a static set of parameters corresponding to a particular fixed set of diagnostic measurements (e.g., an aortic pressure and a pressure taken from a location proximate a stenosis). Thus, one type of monitor is utilized to process and display sensed pressure within a blood vessel. Another type of monitor provides output relating to blood flow within a vessel. As new intravascular diagnostic devices are developed, yet other special-purpose monitors/consoles are developed to display to a physician the sensed parameters.
There is substantial interest in simplifying every aspect of the operating room to reduce the incidence of errors. As one can imagine, the aforementioned intravascular pressure sensors are utilized in operating room environments including many types of sensors and equipment for diagnosing and treating cardiovascular disease. Clearly, the room for error is very limited when performing such activities. Notwithstanding the interest to keep equipment and operations simple, there exists a variety of different sensors that are potentially inserted within a human vasculature to diagnose arterial disease (e.g., blockages) and/or monitor vital signs during a medical procedure. The approach taken in the field of interventional cardiac imaging has been to provide multiple, special-purpose monitor consoles. Each monitor type is linked to a particular type of sensor device.
In a known prior intravascular pressure sensor-to-physiological monitor interface arrangement, marketed by JOMED Inc. of Rancho Cordova, Calif., a physiology monitor receives and displays, on a permanently configured display interface, a set of pressure values corresponding to two distinct pressure signals that are received by the monitor. A first pressure signal is provided by an aortic pressure sensor, and a second pressure signal corresponds to a pressure sensed by a distally mounted solid-state pressure sensor mounted upon a guide wire. The display interface of the monitor is permanently configured to output parameter values corresponding to those two signals. Thus, if display of, for example, a flow signal value is desired, then a separate monitor, such as JOMED Inc.'s FloMap, is used.